Semiconductor fabrication processes are typically conducted with the substrates supported within a chamber under controlled conditions. For many purposes, semiconductor substrates (e.g., wafers) are heated inside the process chamber. For example, substrates can be heated by direct physical contact with an internally heated wafer holder or “chuck.” “Susceptors” are wafer supports used in radiantly heated systems where the wafer and susceptors absorb radiant heat.
Some of the important controlled conditions include, but are not limited to, fluid flow rate into the chamber, temperature of the reaction chamber, temperature of the fluid flowing into the reaction chamber, and temperature of the fluid throughout the fluid line.
In order to obtain a consistent reaction environment, maintaining the correct flow rate of precursor at a correct temperature is among the key factors. However, the importance of maintaining the temperature of the precursors at a uniform temperature is not limited to just the reaction chamber. A number of precursors have a limited temperature range of gaseous phase composition. Thus, in order to maintain the correct flow rate, the precursor must be maintained within a slim temperature range from the source container, through the fluid line, and finally into the reaction chamber.
A number of heater jackets have been developed in an attempt to maintain consistent fluid temperatures during the transition from the temperature controlled source container to the reaction chamber. One common example is cloth heater jackets which surround the fluid line and include a cloth inner layer in contact with the fluid line. The cloth heater jacket may be generally flexible but wear easily. An alternative to heater jackets includes heat tape, which is inexpensive but time consuming to install on fluid lines. Further, when a section of the fluid line needs to be worked on or replaced, the heat tape must be removed, scraped, and a new section installed in its place.
Precursor valve assemblies also present a number of heating challenges due to their compact nature and exposed fluid line connections between each of the valve members or bodies.